Medical Definition of agar
1: a gelatinous colloidal extractive of a red alga (as of the genera Gelidium, Gracilaria, and Eucheuma) used especially in culture media or as a gelling and stabilizing agent in foods
2: a culture medium containing agar
Seen and Heard
What made you want to look up agar? Please tell us where you read or heard it (including the quote, if possible).